Human extraocular muscle (EOM) is selectively susceptible to a large number of sporadic and inherited disorders. In the vast majority of these disorders, neither the etiology nor the selectivity for EOM involvement is understood. These questions have been particularly difficult to address in EOM because these muscles are unique and differ from other skeletal muscle both physiologically and structurally. With recent advances in molecular genetics, however, it is now possible to study an inherited disorder by determining the gene and mutation(s) responsible for the disease and studying the defective gene product. This approach has yielded insight into the molecular basis and pathogenesis of disease processes that have otherwise proven difficult to study. The successful application of this approach to a skeletal muscle disease that spares the EOM has been demonstrated with the cloning and characterization of the gene for Duchenne muscular dystrophy. To better understand EOM and its pathophysiology, the applicant is studying an autosomal dominant inherited congenital disorder selective for EOM, referred to as "Congenital Fibrosis of the Extraocular Muscles" (CFEOM). The present proposal aims to isolate and begin the characterization of the gene responsible for CFEOM. A six generation family with CFEOM has been identified by the applicant and DNA has been isolated from 50 family members within five generations. Linkage analysis is being performed using PCR amplified dinucleotide repeat polymorphisms. The specific aims of Phase I of this project are to establish linkage of athe CFEOM disease to a specific chromosomal position and to begin to develop a map of this region. Once linkage has been established within the pedigree, the degree of genetic heterogeneity between families with the same or similar disorders will be determined. If the mutations in other families map to the same locus, these additional meioses will allow further refinement of the localization. YAC clones of this region will be isolated and further CA repeat polymorphisms will be identified and used to construct a detailed linkage map. When the flanking markers are as close as possible, the YAC contig will be the basis for a physical map of the region. In parallel with this molecular genetic approach, the muscle pathology and neuropathology of CFEOM in the pedigree will be more specifically characterized from study of autopsy tissue from affected family members. The specific aims of Phase II are to identify and characterize athe mutated gene. Appropriate cDNA libraries will be constructed. Candidate genes will be identified and new genes will be isolated from the region between the closest flanking markers. These genes will be examined for characteristics consistent with those of the CFEOM gene, and promising candidates will be screened for mutations. The long- range goal is to characterize the function of the CFEOM gene and its protein product and apply this information to the understanding of EOM biology.